well, joining me now is coral davenport, energy and environment correspondent for the national journal. good to see you again. just how hot was it last year? >> alex, the average annual temperature in the u.s. last year was 55.3 degrees. that was about -- that was a degree higher than the last previous record. it was 3.2 degrees higher than the average record -- than the average temperature for the 20th century. another way to think about the temperatures that we saw last year, between 2011 and 2012 we had 16 months in a row that had higher than normal temperatures. the u.s. has never seen a stretch like that since the u.s. government began keeping temperature records in 1895. so that's another way to think about it. it was hot. >> there's definite perspective there. but why's it happening? >> at this point the evidence is pretty clear. it's happening for two reasons. one is cyclical weather patterns obviously contribute to temperature changes. and the other reason is the increase of fossil fuel emissions in the atmosphere. scientists say at this point the evidence is clear, compelling